One conventional developing cartridge mountable in an electro-photographic type image forming apparatus includes a developing agent accommodating portion for accommodating therein developing agent (e.g. toner), a developing roller, and a roller support portion for supporting the developing roller.
One such developing cartridge also includes a cartridge frame including a first frame constituting a lower portion of the cartridge frame, and a second frame constituting an upper portion of the cartridge frame. The second frame is melt-bonded (or welded) to the first frame. In the roller support portion, the melt-bonding portions between the first and second frames are inclined downward toward the developing roller. Further, the roller support portion has a reinforcing portion extending in an axial direction of the developing roller at a position between the melt-bonding portions facing with each other.